Color printers typically use ink sets having three or four color inks. For example, a common ink set includes three ink colors: cyan, magenta and yellow (CMY). Other ink sets add black ink to the basic CMY system, resulting in a CMYK system. Such three and four ink sets produce some colors by overprinting two of the color inks on top of one another. The gamut of overprinting colors available to a given printer is restricted by the properties of the color inks and may not meet the demands of some printing situations.
Other printers, such as higher end printers and digital presses use ink sets having additional ink colors to increase the available color gamut. For example, Pantone's HEXACHROME (CMYKOG) and Hewlett-Packard's INDICHROME (CMYKOV) ink sets offer a wider color gamut than traditional CMYK inks. The addition of Pantone spot colors to an ink set allows printing of specialized logos, for instance, without the need for half toning. Adding light cyan and light magenta to a basic CMYK ink set (CMYKcm) can reduce the appearance of grain in printed images. Even gray scale images can benefit from the use of modified ink sets, such as an ink set consisting of black along with one or more levels of gray.